It is usually one of the F1 – F12 keys or the DEL key (F2 and DEL are popular). During system start up, you will see a message similar to one of the following: Turn your computer back on and be ready to react quickly.A soft restart will not clear memory and the BIOS setup might not appear. Place the CD/DVD in your drive or insert the USB key as appropriate.
While the specifics vary from computer to computer, the following steps should be of use to most users: To make this change, you first have to access your computer’s BIOS configuration utility. In most cases, this will require you to manually prioritize the CD/DVD/USB as the boot drive ahead of your usual C: drive. After using the CRD ISO to create your bootable CD/DVD/USB drive, you next need to make sure the BIOS is set to boot from the correct drive.